The owner or operator of an underground storage tank with a spill containment structure designed to prevent a release in the event of a spill or overfill while a hazardous substance is being placed in the tank shall annually test the spill containment structure to demonstrate that it is capable of containing the substance until it is detected and cleaned up.
Source:
Section 25284.2, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC§ionNum=25284.2..